Drum Magazine

ABSTRACT

Drum magazines have a body defining an interior and having a rear wall, a rotor rotatably mounted within the interior of the body, the rotor having a periphery defining a plurality of cartridge-receiving spaces, the rotor positioned to define a rim path proximate the rear wall, such that rims of cartridges received by the rotor periphery are proximate the rear wall, and a first rim-engagement element within the interior of the body and proximate the rim path, such that the rims of cartridges passing by the first element are contacted to axially shift each cartridge with respect to a subsequent cartridge. The first rim-engagement element may be a raised protrusion on the body. The rims of cartridges passing by the first rim-engagement element may be contacted to actually shift each cartridge rearward with respect to a subsequent cartridge.

FIELD OF THE INVENTION

The present invention relates to firearms, and more particularly to a drum magazine for rimmed ammunition.

BACKGROUND OF THE INVENTION

A drum magazine is a type of firearms magazine that is cylindrical in shape, similar to a drum. Instead of rounds being stored flat, as in a more common box magazine, rounds in a drum magazine are stored in a circle around the center of the magazine, facing the direction of the barrel. Drum magazines for rimmed ammunition, including shotgun shells, primarily run off a cogged (gear-shaped) design which feeds each individual round of ammunition from the outermost edge of the shell. Recently, a single stack compact design has been developed that uses most of the interior capacity of the drum. It is driven by a single hub and a telescopic shaft.

The advantage over traditional box-shaped magazines is that a drum magazine can carry much more ammunition, often two to three times that of a box magazine, without making it too big to be impractical to carry. The downside to drum magazines is that they increase the overall weight of the weapon in which they are being used, and they are more prone to jamming because of rim lock when used with rimmed ammunition. Shotgun shells have a wide variation in tolerances for overall length, so they are processed and positioned based on contacting their rims.

Rim lock is caused by the rims of improperly stacked shotgun shells impeding each other from feeding into the firearm. Rim lock occurs when the rim of the uppermost shell is positioned behind the rim of the shell immediately below. As a result, the uppermost shell cannot feed forward into the firearm, resulting in a jammed magazine.

Therefore, a need exists for a new and improved drum magazine that prevents rim lock of rimmed ammunition, especially shotgun shells. in this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the drum magazine according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing the additional capacity of a drum magazine while preventing the rimmed ammunition from jamming.

SUMMARY OF THE INVENTION

The present invention provides an improved drum magazine, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide an improved drum magazine that has all the advantages of the prior art mentioned above.

To attain this, the preferred embodiment of the present invention essentially comprises a body defining an interior and having a rear wall, a rotor rotatably mourned within the interior of the body, the rotor having a periphery defining a plurality of cartridge-receiving spaces, the rotor positioned to define a rim path proximate the rear wall, such that rims of cartridges received by the rotor periphery are proximate the rear wall, and a first rim-engagement element within the interior of the body and proximate the rim path, such that the rims of cartridges passing by the first element are contacted to axially shift each cartridge with respect to a subsequent cartridge. The first rim-engagement element may be a raised protrusion on the body. The rims of cartridges passing by the first rim-engagement element may be contacted to actually shift each cartridge rearward with respect to a subsequent cartridge. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front isometric view of the current embodiment of the drum magazine constructed in accordance with the principles of the present invention.

FIG. 1B is a rear isometric view of the current embodiment of the drum magazine constructed in accordance with the principles of the present invention.

FIG. 2A is a rear sectional view of the current embodiment of the drum magazine constructed in accordance with the principles of the present invention.

FIG. 3A is a rear isometric view of the current embodiment of the drum magazine of the present invention with the rear cover removed.

FIG. 3B is an enlarged isometric view of the drum magazine of FIG. 3A.

FIG. 4A is a bottom sectional view of the current embodiment of the drum magazine of the present invention.

FIG. 4B is a front isometric view of the current embodiment of the rear cover and a portion of the tower removed from the drum magazine of the present invention.

The same reference numerals refer to the same parts throughout the various figures.

DESCRIPTION OF THE CURRENT EMBODIMENT

An embodiment of the drum magazine of the present invention is shown and generally designated by the reference numeral 10.

FIGS. 1A and 1B illustrate the improved drum magazine 10 of the present invention. More particularly, the drum magazine 10 has a drum housing 12 with a removably attached rear cover 48 and an upwardly extending tower 22.

The drum housing 12 is a hollow cylindrical body having a closed front 14, an open rear 16, a perimeter 18, and an interior 64 (shown in FIGS. 2A-3B). The front defines a central aperture 20, which may be hexagonal shaped in the current embodiment. The central aperture receives a nut 44 that is threadedly attached to the threaded portion 46 of a bolt 44. The perimeter defines latch ledges 58 that extend outwardly from the rear of the perimeter. A portion of the perimeter defines an opening 106 that receives the bottom 30 of the tower 22. In the current embodiment, the drum housing is made of black plastic.

The tower 22 also has a front 24, a rear 26, a top 28, and a hollow interior 86 (shown in FIG. 2B). The top of the tower has an opening 32 that communicates with the hollow interior of the tower, which in turn communicates with the hollow interior 64 of the drum housing 12. The opening is defined by rear lips 34 and front lips 36. The tower defines a ramp 42 in front of and below the front lips 36. The lips and ramp serve to guide the front 40 of rimmed cartridges 38 forward and upward as the cartridges are fed into a firearm (not shown) attached to the tower. The rear of the tower 56 has a toothed ledge 56 that engages a magazine well latch in the firearm to releasably secure the drum magazine 10 to the firearm. In the current embodiment, the tower is made of black plastic and is illustrated as being manufactured in two pieces. However, the tower can also be manufactured as a single piece or integrally with the drum housing. In the current embodiment, the cartridges 38 are .410 bore shotgun shells.

The rear cover 48 has a front 100, rear 102, and an interim 98 (shown in FIG. 4A). The rear defines a central aperture 52 that receives the head portion 54 of the bolt 44. The rear cover removably closes the open rear 16 of the drum housing 12. The rear Cover has latches 50 that extend forward from the front and engage the latch ledges 58 on the drum housing 12. In the current embodiment, the rear cover is made of transparent plastic so the quantity of shells remaining in the drum magazine 10 can be easily viewed.

FIGS. 2A-3B illustrate the improved drum magazine 10 of the present invention. More particularly, the drum magazine is shown with the rear cover 48 removed so the interior 64 of the drum housing 12 is visible. The perimeter 18 of the interior 64 of the drum housing forms a rearwardly extending primary guide bump 90 that will be discussed in further detail after the description of FIGS. 4A and 4B. The front of the drum housing forms a rearwardly protruding central axle 108 that receives the hub 76 of a rotor 60. The hub 76 has a central aperture 80 that receives the head portion 54 of the bolt 44. The rotor is free to rotate about the axle, but is prevented from axial movement by the engagement of the bolt with the nut 44.

The rotor 60 has a front sprocket 72 and a rear sprocket 66 that are connected to the hub 76 by spokes 62. The front sprocket has teeth 74 that define cartridge-receiving spaces in the form of recesses 76. The rear sprocket has teeth 68 that define cartridge-receiving spaces in the form of recesses 70. The recesses are paired to receive the fronts 40 and rears 82 of the shotgun shells 38. The front sprocket is slightly offset clockwise with respect to the rear sprocket so that the front of each shell is positioned to the right of the rear of each shell. The rear of each shell forms a rim 84. The center to center spacing of the recesses is greater than the diameter of the rims of the shells. In the current embodiment, the sprockets, spokes, and hub are manufactured as a single integral part.

As the rotor 60 rotates in a clockwise direction, the shotgun shells are directed upwards into the interior 86 of the tower 22 by the guide plate 84. Rotation of the rotor is limited by a radially protruding stop 88 when the stop encounters a guide plate 84 that is attached to the interior of the drum housing below the opening 106. This state occurs when the drum magazine 10 has been emptied and needs to be reloaded.

FIGS. 4A-4B illustrate the improved drum magazine 10 and rear cover 48 of the present invention. More particularly, the interior 98 of the rear cover 48 forms a forwardly extending secondary guide bump 96 immediately below opening 104. When the rear cover is attached the drum housing 12, the opening 104 is aligned with the opening 106 in the drum housing so that shells 38 can be fed upward by the guide plate 84 into the interior 86 of the tower 22.

Referring now to FIGS. 2A, 3A, 3B, and 4A, the rim lock prevention features of the drum magazine 10 will now be described. The primary guide bump 90 and secondary guide bump 94 prevent rim lock of the shells 38 by occurring in the following manner by serving as rim-engagement and separator elements. Initially, the recesses 70, 76 in the sprockets 66, 72 space apart the shells 38 so their rims 84 do not engage. As the rotor 60 rotates clockwise, the movement of the rims defines a rim path proximate the cover, and the primary guide bump located on the drum housing 12 slightly nudges the rim of shell 92 rearward into a separate plane from that of shell 94. At the same time, the secondary guide bump located on the rear cover 48 nudges the rim of shell 94 forward. Shell 94 is the shell proximate the guide plate 84, and shell 92 is the shell located immediately clockwise of shell 94. As a result, the rim of shell 94 is stacked in front of the rim of shell 92 within the tower 22. Therefore, as shell 94 is pushed forward and upward as the shell 94 exits the opening 32 in the top 28 of the tower, the rim of shell 92 does not impede the forward feeding motion of shell 94. As a result, rim lock does not occur, and the drum magazine does not jam as each round of ammunition is fed into the firearm.

The rim lock prevention features of the drum magazine 10 enact their forces and force alignment to prevent rim lock just before, and at the time of each shell's transition, from the divided sprocket cogs 70, 76 to direct shell-to-shell contact and tension. The manipulation of the shells 92, 94 is only possible before the transition to tension, which occurs the moment the shells leave the support of the drum sprocket cogs and are forced upon each other. After this occurs, further manipulation of the shell rims is impossible.

In the context of the specification, the terms “rear” and “rearward,” and “front” and “forward” have the following definitions: “rear” or “rearward” means in the direction away from the muzzle of the firearm while “front” or “forward” means it is in the direction towards the muzzle of the firearm.

While a current embodiment of a drum magazine has been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 

I claim:
 1. A magazine for a firearm operable to receive rimmed cartridges, the magazine comprising: a body defining an interior and having a rear wall; a rotor rotatably mounted within the interior of the body; the rotor having a periphery defining a plurality of cartridge-receiving spaces; the rotor positioned to define a rim path proximate the rear wall, such that rims of cartridges received by the rotor periphery are proximate the rear wall; and a first rim-engagement element within the interior of the body and proximate the rim path, such that the rims of cartridges passing by the first element are contacted to axially shift each cartridge with respect to a subsequent cartridge.
 2. The magazine of claim 1 wherein the first rim-engagement element is a raised protrusion on the body.
 3. The magazine of claim 1 wherein the rims of cartridges passing by the first rim-engagement element are contacted to axially shift each cartridge rearward with respect to a subsequent cartridge.
 4. The magazine of claim 1 further comprising: a second rim-engagement element within the interior of the body and proximate the rim path, such that the rims of cartridges passing by the second element are contacted to axially shift each cartridge with respect to a subsequent cartridge.
 5. The magazine of claim 4 wherein the second rim-engagement element is a raised protrusion on the rear wall.
 6. The magazine of claim 4 wherein the rims of cartridges passing by the second rim-engagement element are contacted by the second element when the rim of a subsequent cartridge passing by the first rim-engagement element is contacted by the first element.
 7. The magazine of claim 4 wherein the rims of cartridges passing by the second rim-engagement element are contacted to axially shift the each cartridge forward with respect to a subsequent cartridge.
 8. The magazine of claim 1 wherein the cartridge-receiving spaces in the rotor are spaced apart to position the rims of the cartridges so the rims are free to move forward and rearward with respect to one another.
 9. The magazine of claim 1 wherein the center to center spacing of the cartridge-receiving spaces is greater than the diameter of the rims of the cartridges.
 10. The magazine of claim 1 wherein the cartridge-receiving spaces in the rotor position a forward portion of the cartridges to the right of the rims of the cartridges.
 11. The magazine of claim 1 wherein the rear wall is a removable cover.
 12. The magazine of claim 1, further comprising an arcuate guide plate mounted within the interior of the body.
 13. The magazine of claim 12, wherein the guide plate guides the cartridges upwards as the cartridges engage the guide plate. 